The present invention concerns a spark plug of an internal combustion engine, in particular for use in Otto-cycle gas engines, comprising an insulator body, a base central electrode, at least one ground electrode and at least one swirl chamber, wherein the electrodes of the spark plug are surrounded by a wall, which in particular is in the form of a surface of a cylinder, of the swirl chamber. The invention further concerns a process for producing a spark plug.
The spark plugs which are available at the present time for industrial gas engines are in many cases products which were derived from the automobile industry and adapted by suitable improvements for the preferential use in industrial gas engines. Those spark plugs generally have a cylindrical central electrode which is provided with a precious metal pin. In regard to the ground electrodes, both configurations with a hook electrode and also configurations with between two and four laterally disposed electrode fingers are in use. The hook electrodes can also be provided with a precious metal plate portion. Such spark plugs are known for example from EP 0 834 973 A2, EP 0 859 436 A1, EP 1 049 222 A1, DE 196 41 856 A1 and WO 95/25372. The disadvantage of those spark plugs is essentially inter alia that the flow conditions in the region of the ignition location depend entirely on the flow conditions in the combustion chamber of the respective cylinder. Thus for example the ignition spark can be blown out if the flow speeds of the gas-air mixture are excessively great.
In order to eliminate that disadvantage, it is already known from U.S. Pat. Nos. 5,554,908 A, 2,776,394 A and FR 2 131 938 A for the electrodes of the spark plug to be surrounded by a cylindrical swirl or turbulence chamber. The arrangement illustrated in U.S. Pat. No. 5,554,908 A however suffers inter alia from the disadvantage that it does not have any defined ground electrodes and the ignition sparks are propagated between the central electrodes and any point on the swirl chamber which functions as a ground electrode. In the case of the spark plugs shown in U.S. Pat. No. 2,776,394 A and FR 2 131 938 A there is the disadvantage that there are in each case only one or two ground electrodes of small area, which have comparatively short service lives and which rapidly become useless due to wear or fouling.